Treatment of Streptococcus equisimilis Meningitis
For Streptococcus equisimilis (Group C/G streptococcus) growth in CSF, treat immediately with high-dose intravenous penicillin or ceftriaxone plus vancomycin as empiric therapy, following standard bacterial meningitis protocols, as these organisms are uniformly susceptible to beta-lactams and delay in treatment significantly increases mortality. 1
Immediate Antibiotic Management
Empiric Therapy (Before Susceptibilities Available)
Start treatment within 1 hour of clinical suspicion - delay is strongly associated with death and poor neurological outcomes 1. The regimen depends on patient age:
Adults <60 years: Ceftriaxone 2g IV every 12 hours (or cefotaxime 2g IV every 6 hours) PLUS vancomycin 15-20 mg/kg IV every 8-12 hours 1
Adults ≥60 years or immunocompromised: Add ampicillin 2g IV every 4 hours to cover Listeria, in addition to the above regimen 1
Infants 8-60 days old: Ampicillin 300 mg/kg/day IV divided every 6 hours PLUS ceftazidime 150 mg/kg/day IV divided every 8 hours 2
Definitive Therapy (After Organism Identification)
Once S. equisimilis is confirmed, narrow to high-dose penicillin G or continue ceftriaxone 3. These organisms are uniformly susceptible to penicillin, though treatment failures have been reported 3.
- Penicillin G: 24 million units/day IV divided every 4 hours (standard for streptococcal meningitis)
- Alternative: Continue ceftriaxone at meningitis dosing (2g IV every 12 hours for adults) 1
- Duration: 10-14 days minimum for streptococcal meningitis 1, 4
Adjunctive Dexamethasone
Administer dexamethasone 10mg IV every 6 hours immediately before or simultaneously with the first antibiotic dose 1. Continue for 4 days if streptococcal meningitis is confirmed 1. This reduces mortality and neurological morbidity in bacterial meningitis 1.
Critical Monitoring Parameters
CSF Follow-up
- Repeat lumbar puncture at 48-72 hours if clinical deterioration occurs or fever persists 4
- Monitor CSF cell count, glucose, protein, and cultures to assess treatment response 4
- Continue antibiotics until CSF is sterile and inflammatory parameters improve 4
Clinical Red Flags
S. equisimilis can cause severe invasive disease similar to S. pyogenes 3, 5:
- Toxic shock-like syndrome: Watch for rapidly evolving shock, multiorgan failure - may require IVIG as salvage therapy 6
- Vascular complications: White matter lesions and even dural arteriovenous fistulas have been reported after CNS infection 7
- High mortality in elderly: Case fatality rates of 15-18% in bacteremia, higher with underlying comorbidities 5
Antibiotic Resistance Considerations
Important caveat: While penicillin resistance is not reported, 16.2% of S. dysgalactiae subsp. equisimilis isolates show clindamycin resistance 8. Additionally, resistance to tetracyclines and macrolides occurs 3.
- Do not use clindamycin as monotherapy without susceptibility confirmation 8
- Penicillin/ceftriaxone remain the drugs of choice 3
- Vancomycin in the empiric regimen provides coverage until organism identification 1
Special Circumstances
If Shunt-Associated Meningitis
If the patient has a VP shunt or other CSF device:
- Remove all infected shunt components and place external ventricular drain 4
- Success rates are significantly lower when attempting to treat with shunt in situ 4
- Continue antibiotics for 21 days for gram-negative organisms, 10-14 days for streptococci 4
- Reimplant new shunt only after CSF sterility is achieved 4
If CSF Leak Present
- Do not delay antibiotics for surgical repair of CSF rhinorrhea 9
- Complete full antibiotic course (10-14 days) before considering surgical repair 9
- Surgical repair should be performed after infection control to prevent recurrent meningitis 9
Common Pitfalls to Avoid
- Delaying antibiotics for imaging: Start treatment immediately on clinical suspicion, obtain CT only if high-risk features present (altered mental status, focal deficits, papilledema) 1
- Underestimating severity: S. equisimilis can cause toxic shock syndrome and invasive disease comparable to S. pyogenes 3, 6
- Stopping vancomycin too early: Continue vancomycin until organism identification confirms it is not S. pneumoniae 2
- Inadequate dosing: Use meningitis-dose antibiotics (higher than for bacteremia) to achieve adequate CSF penetration 1